471 The objective of this study is to characterize the pharmacokinetic profile of nalmefene and its metabolite, nornalmefene, in hepatically impaired (mild, moderate, and severe) subjects and age, gender, and weight matched healthy controls. This study will also determine the influence of liver dysfunction on nalmefene protein binding, and evaluates the possible relationships between nalmefene disposition and the Pittsburgh cocktail, used as metabolic probes for specific drug metabolizing enzymes.